期刊
ADVANCED ENERGY MATERIALS
卷 12, 期 1, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/aenm.202102172
关键词
bulk heterojunctions; fluorination; morphology control; non-fullerene solar cells
类别
资金
- US Office of Naval Research [N00014-20-1-2116]
- US Department of Commerce, National Institute of Standards and Technology, Center for Hierarchical Materials Design Award [70NANB19H005]
- Qatar National Research Foundation [NPRP12S-0304-190227/02-484761]
- P.R.C. Sichuan Province Key Laboratory of Display Science and Technology
- National Science Foundation Materials Research Science and Engineering Center (MRSEC) at Northwestern University [NSF DMR-1720139]
- National Science Foundation [NSF CHE-1048773]
- Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource [NSF NNCI-1542205]
- MRSEC Program of the Materials Research Center at Northwestern University [NSF DMR-1720139]
- Department of Energy [DE-AC02-05CH11231]
- DOE Office of Science [DE-AC02-06CH11357]
- Sichuan Province Key Laboratory of Display Science and Technology
- China Scholarship Council [201906070056]
In this study, the fluorination of the NFA end group was systematically investigated to understand how it affects the morphology and photovoltaic performance of the blend. The results showed that highly fluorinated NFA molecules can improve the BHJ morphology, enhance NFA-cathode contact, and enhance the photovoltaic performance of the OSC.
Non-fullerene acceptor (NFA) end group (EG) functionalization, especially by fluorination, affects not only the energetics but also the morphology of bulk-heterojunction (BHJ) organic solar cell (OSC) active layers, thereby influencing the power conversion efficiency (PCE) and other metrics of NFA-based OSCs. However, a quantitative understanding of how varying the degrees of NFA fluorination influence the blend morphological and photovoltaic properties remains elusive. Here a series of three A-DAD-A type NFAs (D = pi-donor group and A = pi-acceptor EG) which systematically increase the degree of EG fluorination and comprehensively investigate the resulting blends with the polymer donor PM6 in terms of optical properties, electronic structure, film crystallinity, charge carrier transport, and OSC performance is reported. The results indicate that the most highly fluorinated NFA, BT-BO-L4F, achieves an optimal BHJ hierarchical morphology where enhanced NFA molecule intermolecular pi-pi stacking and optimal vertical phase gradation are achieved in the BHJ blend. These factors also promote optimum NFA-cathode contact, more balanced electron and hole mobility, and suppress both monomolecular and bimolecular recombination. As a result, both the short-circuit current density and fill factor in this OSC series progressively increase with increasing EG fluorine density, and the resulting PCEs increase from 9 to 16.8%.
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